Sealing ultralow $κ$ porous dielectrics with thin boron carbonitride films

Porous ultralow $κ$ dielectric film pores were sealed by $1–5nm$ films of boron carbonitride, itself a dielectric. The $BC0.9N0.07$ films were deposited by chemical vapor deposition at $335°C$ on etched and ashed blanket films and patterned films of porous methyl silsesquioxane (PMSQ). The penetration of Ta through the boron carbonitride film and into the porous low $κ$ substrate following exposure to $TaF5$ at $230°C$⁠, or $TaSix$ growth from $TaF5$ and $Si2H6$ at $230°C$⁠, was used to test pore sealing. Tantalum profiles were evaluated using x-ray photoelectron spectroscopy depth profiling, back side secondary ion mass spectroscopy, and energy dispersive x-ray spectroscopy. A $3.9nm$ boron carbonitride film sealed PMSQ, which has an average pore diameter of $1.9nm$ before etching. The diffuse nature of the $BC0.9N0.07$-PMSQ interface in electron energy loss profile maps suggests that some of the $BC0.9N0.07$ penetrates into the PMSQ until the pore openings are pinched off as the sealing film deposits.